Control system for industrial vibrating machinery



J -m. 26, 1943. D. B. CLARK 2,309,098

CQNTROL SYSTEM FOR INDUSTRIAL VIBRATING MACHINERY Filed Sept. 14, 1940 INVENTOR; DUDLEY E. CLARK BY D 9 ATTORNEYS.

Fig.4

Patented Jan. 26, 1943 CONTROL SYSTEM FOR INDUSTRIAL VIBRATIN G MACHINERY Dudley B. Clark, Palm Springs, Califl, assignor to The W. S. Tyler Company, Cleveland, Ohio, a

corporation of Ohio Application September 14, 1940, Serial No. 356,863

6 Claims. (Cl. 250-27) This invention relates to a control system for industrial vibrating machinery.

In Weyandt Patent No. 1,655,482, there is disclosed a system for vibrating industrial screens, in which there is selected from a source of alternating current by asymmetrical conduction, through the use of a vacuum tube or electrolytic valve, successive spaced unidirectional current impulses effecting successive movements of the screen in the same direction. Operating on a commercial frequency of 60 cycles per second, there is produced in this manner, 3600 vibrations of the screen per minute. This has been generally satisfactory for light work on single surface screens, but has not proved satisfactory for heavy work, or where more than one surface has to be vibrated by means of a single vibrator. It has, accordingly, been necessary heretofore, to confine the use of the Weyandt 60 cycle system to a relatively narrow field of fine screening in single surface units, and to employ for heavier work and for use with the larger vibrators, low frequency, 1. e., 15 cycle, motor-generator sets, which are objectionable, both from the standpoint of cost, and from the standpoint of other disadvantages and defects referred to in said Weyandt patent.

The invention accordingly has as its primary object, the provision of a power supply which is particularly adapted for heavy screening and for use with the larger vibrators, which is relatively low in cost, and is free from the disadvantages and defects which characterize the use of motor-generator sets and the like.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described, and particularly pointed out in the claims; the annexed drawing and the following description setting forth in detail certain means for carrying out the invention, such disclosed means illustrating, however, but one of various ways in which the principle of the invention may be used.

In said annexed drawing:

Fig. 1 is a schematic diagram of an electrical circuit embodying the novel features of the invention;

Fig. 2 is a diagrammatic view of the electrical circuit of Fig. 1, including details of the timing unit;

Fig. 3 is an oscillogram of the voltage waves supplied to the electromagnet of the screen in the circuit illustrated in Figs. 1 and 2, and

I A. C. source.

the timing unit utilized in the circuit of Figs. 1 and 2.

Referring more particularly to the drawing, the circuit includes as its principal part a source of alternating current, the terminals of which are designated A and B, a vibrating screen or other load L, a power tube PT and a timing unit or timer T.

The screen L is in a line extending from the terminal A to the anode I of the power tube, which power tube further includes an electron emitting body or cathode 2 and a grid 3. The cathode is energized by means of a transformer T1, which derives its energy from the terminals A and B of the alternating current circuit.

The tube PT is. selected in accordance with the amount of power required by the load, but for loads up to its capacity, the hot cathode triode is preferred, and for larger loads an igniter type cold cathode tube is connected with its anode-igniter path directly across the triode.

The transformer T1 is a cathode filament heating unit. A small potential bias may be inserted in the grid circuit of the .tube PT.

The timing unit includes as its principal parts a small series transformer T2, and a three element control tube CT. The cathode l of the tube CT'is indirectly heated by means of a transformer T3, which derives its energy from an A rectifier tube RT, is also provided, the cathode 5 of which is energized by means of a transformer T4, which also derives its energy from an A. C. source.

The anode 6 of the tube CT is connected to one end of the secondary coil of a tramformer T5, which is preferably a small insulating transformer, the primary coil of which is placed across the lines extending from the terminals A and B. The other end of the secondary coil of the transformer T5 is connected to one end of the primary coil of the series transformer T2, a fixed resistor R1, being inserted in the line connecting said secondary and primary coil. The other end of the primary coil of the transformer T2 is connected to the cathode l of the tube CT. Thus the primary of the transformer T2 is in series with the plate-filament circuit through the tube CT with the secondary coil of the transformer T5 as a source of potential therefor.

One end of the secondary coil of the transformer T2 is connected to the anode 8 of the tube RT, and the other end of the said coil is connected to the grid 9 of the tube CT, as well as to the grid 3 of the tube PT, a fixed resistor 4 is a S p fi d d m tic View of 55 R2 and a source of biasing potential 132 being connected in series in the line leading to the grid 3, and a similar resistor R3, being inserted in the line leading to the grid 9.

The timing unit further includes a condenser or capacitor C, preferably of 4 mi., an adjustable resistance R4, and a bias B. As shown, the resistor R4 and the condenser C are shuntconnected with each other whereby adjustment of the value of the resistor will determine the duration of the discharge period of the condenser after the latter has become charged as the result of a positive current impulse passing through the tube CT. The parallelly-connected condenser C and the resistor R4 are connected between that end of the secondary coil of the transformer T2 which is connected to the grid elements 3 and 9 and the positive terminal of the biasing battery 13, the negative terminal of said battery being connected to that end of the primary of transformer T2 which has previously been described as being connected to the cathode of the tube CT. Thus the grid elements 3 and 9 of the tubes PT and CT, respectively, are normally biased by potential sources B2 and B, but these potentials are overcome during discharge periods of the condenser.

In Fig. 4, the reference characters and C1 are the terminals leading to the grid and cathode of any power tube which it is desired to control.

The polarities which are indicated in the drawings are, it will be readily understood, instantaneous polarities.

Having thus described the general make-up of the electrical circuits, the action which occurs therein will now be described.

When the terminal A is plus, the power tube PT and the control tube CT both conduct, producing impulse #l, as shown in Fig. 3. On the other half of this same cycle, tubes PT and CT will not conduct, so that impulse #2 is automatically omitted. During impulse #1, condenser C received a charge which can only leak off in a definite period of time, determined by the setting of the rheostat R4. Impulse #3 (Fig. 3) is therefore omitted, due to a negative charge on the control grids of the tubes CT and PT. Impulse #4 is again automatically eliminated, but during the time which elapsed during the half cycle of impulse #4, the charge on the condenser C has been completely absorbed by the rheostat R4, eliminating the negative charge on the control grids of the tubes CT and PT, thus allowing impulse #5 to be impressed on the load in the same manner as was impulse #1. 1800 vibrations per minute are caused to be imparted to the screen or other vibratory equipment, it being understood that impulses 6, 1 and 8 are omitted, impulse #9 impressed on the load, etc.

If desired, the line K to Y, and the line D, may be omitted by using the optional method of connecting terminals X and G to the cathode and grid respectively of the tube P'I'.

Referring to the timing unit, it may be pointed out that the tube CT can be eliminated by feeding its grid circuit directly to the power tube and placing a transformer in series with the power tube. It will be noted however, that this will require a different adjustment of the rheostat R4. for every change in the amount of current passing through the tube PT.

By using the timer or control unit as shown, it will control a number of power tubes at the same time, while feeding into one or more vibrators without change of adjustment.

In this way, I

The tube RT is a small rectifier tube. the purpose of which is to stop the condenser C from discharging except through the time constant of the rheostat R3.

The tube CT may be a 3 or 4 element gas tube, such as an RCA 885 saw tooth gas oscillator, utilizing a 5 prong base. The value of the fixed resistor R, is chosen to keep the anode current of the tube CT at only a fraction of its rated capacity. Both of these control tubes are loaded very lightly in respect to average and peak current ratings and should, therefore, have an exceptionally long life.

There is a distinct difference in the reason for using the bias on the tube PT, as compared with the reason for the use of the bias on the tube CT. For example, it is desired to hold the power tube non-conducting for one full cycle or more, by virtue of the negative charge on the grid of this power tube, in relation to its cathode. In other words, the bias will hold it negative at all times, in which it does not receive an over powering positive impulse, from its timing tube circuit. The exact reverse of this is true in the case of the control tube CT, which, as will be noted from Fig. 2, is held positive at all times except when overcome by the negative influence of the C--R4 combination.

It may be further noted that an increase of resistance at B4 will decrease the frequency of the vibrating rectified impulses, so that it is possible in this way, to skip or omit the impulses between, say, impulses I and 1.

All of the tubes are preferably gas-filled, that is, they contain a low pressure of inert gas, such as helium, xenon, mercury, neon, etc. A vacuum tube in this circuit will not only fail to carry the power required, but will act in a far different manner, viz., when capacitor C charges, a vacuum tube grid would stop the flow of power on impulse #l before the impulse was fairly begun, while a gas tube acts with a trigger impulse, and once started with a positive charge (or in some cases with a less negative charge) on its grid, the grid at once loses all control, and nothing can stop the flow of power through the tube until the anode becomes negative at the end of the half cycle, after all of impulse #I has been completed.

If the setting of R4 is such that the grid of the control tube is held negative part way into impulse #5, voltage control is obtained by means of phase displacement between grid and anode voltages. This can be continued until impulse #5 is wiped out entirely, at which time the vibrator will drop into 1200 V. P. M. (vibrations per minute), or 20 cycles. If this is carried still further, the voltage will again be cut down until 900 V. P. M. is reached, and so on. This verifies the fact that a gas tube can be delayed in starting to a very accurate degree, but once started, a reversal of line current, only, will stop it. This explains the voltage control feature obtained in this circuit, which provides both control over the number of vibrations in a given time, as well as the average power delivered to the vibrator, without the use of power wasting rheotats inserted in the line.

Referring to Fig. 3, it is apparent that the more impulses that are skipped, the lower the number of vibrations per minute, but that the frequency will never become zero. Around 15 and 20 cycles, the telephone ringing frequencies are approached, which suggests that the present circuit may be substituted for motor-generator in telephone central stations.

It is thus seen that I have provided means for effectively producing a rectified impulse power supply for vibrating machinery operating at a frequency of half or less than the frequency of the normal supply line.

Other forms may be employed embodying the features of my invention instead of the one herein explained, change being made as regards the means herein disclosed provided the elements stated by any of the following claims or the equivalent of such tated elements be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A thermionic control system comprising a source of alternating current, an electron tube including plate, filament and grid electrodes, circuit connections between said source and the plate and filament electrodes adapted to energize a load when said tube is conducting, grid biasing means rendering the tube normally conducting for positive impulses of the current only, and means for controlling the grid potential of the tube to vary the frequency of the positive impulses passed by the tube comprising a time network including a thermionic control tube having plate, grid and filament electrodes, circuit connections between said plate and filament electrodes and said source, means for biasing said control tube grid to render the tube conducting to positive impulses of current only, a condenser, a charging circuit for said condenser, said circuit including the plate filament circuit through said control tube, a discharge circuit for the condenser connected to impose an opposing bias upon the grids of said tubes to maintain the tubes non-conducting during the discharge period of said condenser, and means to prevent discharge of said condenser through the charging circuit thereof.

2. The thermionic control system recited in claim 1 wherein said last-mentioned means comprises a one-way conducting electric valve connected in said condenser charging circuit.

3. A thermionic control system comprising a source of alternating current, a plurality of thermionic tubes each including plate, filament and grid electrodes, circuit connections between the source and said plate and filament electrodes of said tubes for rendering the plate electrodes positive simultaneously, grid biasing means for normally rendering the tubes conducting to positive impulses of current only, a condenser, means for charging said condenser including a transformer having a primary winding connected in series with the plate filament circuit of one of said tubes, said transformer including a secondary winding connected in series with said condenser, a resistance shunted across said condenser, and circuit connections between said condenser and the grid elements of said tubes to impose thereon a predominating bias rendering the tubes non-conducting throughout the discharge period of the condenser.

4. A thermionic control system comprising a source of alternating current, a plurality of thermionic tubes each including plate, filament and grid electrodes, circuit connections between the source and said plate and filament electrodes of said tubes for rendering the plate electrodes positive simultaneously, grid biasing means for normally rendering the tubes conducting to positive impulses of current only, a

condenser, means for charging said condenser including a transformer having a primary winding connected in series with the plate filament circuit of one of said tubes, said transformer including a secondary winding connected in series with said condenser, a resistance shunted across said condenser, circuit connections between said condenser and the grid elements of said tubes to impose thereon a predominating bias rendering the tubes non-conducting throughout the discharge period of the condenser, and a oneway conducting electric valve included in the series circuit connecting the secondary winding of said transformer and said condenser to prevent discharge of the condenser through the charging circuit thereof.

5. A thermionic control system comprising a source of alternating current, a power tube including plate, filament and grid electrodes, a control tube including plate, filament and grid electrodes, circuit connections between the source and the plate and filament electrodes of said power tube for energizing the load when the tube is conducting, biasing means for rendering the power tube conducting to positive current impulses only, means for simultaneously impressing on the plate electrodes of said tubes potentials of like polarity from said source comprising a transformer having a primary winding connected to said source and a secondary winding connected to the plate filament electrodes of said control tube, the connection between the secondary winding of the transformer and the filament electrode of said tube including in series the primary winding of a second transformer, a condenser, a charging circuit therefor including the secondary winding of said second transformer, means for controlling the discharge rate of said condenser, and a connection between said condenser and said grid electrodes of the power tube and control tube to thereby impose controlling potentials thereon during the discharge period of the condenser to render the tubes non-conducting.

6. A thermionic control system comprising a source of alternating current, a power tube including plate, filament and grid electrodes, a control tube including plate, filament and grid electrodes, circuit connections between the source and the plate and filament electrodes of said power tube for energizing the load when the tube is conducting, biasing means for rendering the power tube conducting to positive current impulses only, means for simultaneously impressing on the plate electrodes of said tubes potentials of like polarity from said source comprising a transformer having a primary winding connected to said source and a secondary winding connected to the plate filament electrodes of said control tube, the connection between the econdary winding of the transformer and .the filament electrode of said tube including in series the primary winding of a second transformer, a condenser, a charging circuit therefor including the secondary winding of said second transformer, and a one-way conducting electric valve, mean for controlling the discharge rate of said condenser, and a connection between said condenser and said grid electrodes of the power tube and control tube to thereby impose controlling potentials thereon during the discharge period of the condenser to render the tubes non-conducting.

DUDLEY B. CLARK. 

